Musnad Ahmad 5:218

Abu Sa’id, the freed slave of Banu Hashim, narrated to us, Shu’bah narrated to us, from al-Hakam and others, from al-Qasim ibn Mukhaymirah, from Shurayh ibn Hani’, who said: I asked ‘Aishah about wiping over the leather socks (khuffayn). She said: "Ask ‘Ali." So I asked him, and he said: "Three days and their nights for the traveler, and a day and a night for the resident."